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Twitchett, EA, Koutedakis, Y, and Wyon, MA. Physiologic fitness and professional classical ballet performance: a brief review. J Strength Cond Res 23(9): 2732-2740, 2009-Although classical ballet is an artistic expression through the use of the body, there is a real opportunity to improve and extend the dancer's career by simply applying sports science principles to dance training and performance. Dance training is a long process of physical, intellectual, and psychological preparation, through physical exercise, often beginning in childhood and continuing until retirement. Fitness programs, supplementary to traditional dance classes, have only recently been considered as a part of this process; it may be suggested that this cross-training has generally been avoided thus far because of tradition and a reluctance to follow principles associated with sport. Classical ballet training, rehearsal, and performance do not elicit significant stimulus to result in increased aerobic fitness levels. Therefore, dancers often demonstrate low levels of aerobic fitness even though a strong aerobic foundation is necessary to meet the required workload. Dancers have greater than average range of motion and strength at the hip joint but weaknesses in the upper body, torso, hamstrings, and quadriceps. In the past, dancers have been wary of strength training because they perceive this leads to aesthetically undesirable hypertrophy. Dancers also have low body weights and low percentage body fat. Given that training does not provide the opportunity to expend enough energy to maintain these aesthetic demands, this aesthetic demand may be met by caloric restriction, which may lead to subsequent increased injury risk. It has been hypothesized that a “fit for purpose” body can help improve performance, reduce the risk of injury, and ensure prolonged dance careers. This review aims to explore the extent to which physical fitness components relate to dance performance, in particular classical ballet.

1School of Sport, Performing Arts and Leisure, University of Wolverhampton, Wolverhampton United Kingdom; and 2Department of Exercise Sciences, University of Thessaly, Thessaly, Greece

Introduction

There are 2 factors that differentiate dance from sport (38); these are expressivity and extreme range of motion at the ankle and hip joints. However, it may be argued that sports such as artistic and rhythmic gymnastics have similar expressive characteristics and ranges of motion (3). It may also be that the physiologic demands of dance reflect other sports; for example, classical ballet has been defined as predominantly an intermittent type of exercise (55), similar to sports such as soccer and tennis, in which explosive bursts of exercise are followed by moments requiring precision and skill. For that reason, it has been suggested that dancers would benefit from a good aerobic foundation (1) and high anaerobic threshold to limit the effects of blood lactate accumulation such as a decrease in balance, poise, and coordination (3).

An early investigation into physiologic demands of dance reported a dancers' workload of “moderate to heavy,” (15) although the demands of this workload were not specified. More recent work has begun to examine the demands of classical ballet on the body by investigating aspects such as the cardiovascular system, muscular strength and power, flexibility, anthropometry, and agility. To better prepare classical ballet dancers to excel in their art, it is imperative that those working with dancers understand the demands placed on the body so that training can be designed to meet the necessary requirements. Therefore, the main purpose of the present article is to review the current opinion regarding the various demands that classical ballet poses on several fitness systems: the cardiorespiratory system, the muscular system (power, endurance, and strength), and the musculoskeletal system. Fitness levels of classical ballet dancers will be discussed, along with body composition and agility, particularly with regard to meeting the demands of classical ballet repertoire.

Aerobic Demands of Classical Ballet

Class

With the aim of identifying the physiologic demands of the task directly relevant to energy supply mechanisms, classical ballet class has been assessed using established scientific methodology (55). It was found that a traditional ballet class consists of 3 distinctive phases: a) barre exercises, b) center floor exercises of moderate intensity, and c) center floor exercises of higher intensity, including jumps, travelling, and mid-air turns. It was also found that each exercise during the first phase lasted for approximately 60 seconds followed by 30 seconds resting, whereas for the second and third phases, the corresponding values were 35 and 85 and 15 and 75 seconds, respectively. For the same 3 phases, the dancers' oxygen uptake (%O2 max) was found to be 36%, 43%, and 46% of maximum, respectively. These values are similar to those found in a comparable study (17) suggesting that the barre section of a ballet class represents aerobic exercise of low to moderate intensity, and that during center exercises, the intensity increases. However, such intensities of body work are not adequate to stimulate aerobic system enhancements (32). It was also found that dancers' heart rates, studied during ballet class, were below 70% of maximum for long periods of time, peaking at 95% and 85% for males and females, respectively (16).

It should be worth noting that, in these early studies, oxygen uptake was measured using a Douglas bag, which may have restricted movement, thus affecting the final results. It should also be noted that studies using heart rate and oxygen uptake data alone often give incorrect data of the time spent at high intensities because heart rate and oxygen uptake remain elevated after the end of exercise to help recovery (5).

Performance

Oxygen uptake of professional dancers was also assessed during studio and live performances (55,17). During studio performance of specific variations or pas de deux, oxygen uptake averaged 80% of maximum, whereas blood lactate concentration was approximately 10 mM immediately after performance of the variation (55). During performances of ballets before live audiences, heart rates were noted as being frequently close to maximum, (16,55) and the average peak blood lactate value for live performances was 11 mM, slightly higher than those found for studio performances. Oxygen uptake was estimated immediately after the performance and averaged 85% of O2 max, which, again, was slightly higher that for studio performances. However, although these data show that dancers worked at high %O2max, the level was only sustained for very short periods of time, resulting in little, if any, development of the aerobic system (32).

Heart rates of classical ballet dancers during the full length of classical ballet productions on stage were also examined (16). Values increased rapidly during the first 1 to 2 minutes of dancing and often approached near-maximal levels. During the allegro (jumping) sections of performance, the mean peak heart rate for all subjects reached 94% of maximum. These values are similar to heart rate responses during strenuous athletic events such as short and middle distance running. The work-rest ratios during allegro sections ranged from 1:1.6 to 1:3, which are similar to those seen in racquet sports such as squash or tennis (23). Slower adagio sections, which are lower in intensity and involve balances and controlled movements, were sustained for longer periods and produced lower heart rates compared with allegro sections. However, there were no instances in which dancing was sustained at a level of cardiovascular stress that may be classified as aerobic endurance exercise (16).

More recent work in this area has since questioned the use of heart rate as a predictor of O2 in dance (51). This does mean that, to date, there has been little, or no, research investigating the cardiorespiratory demands of classical ballet performance in which true gas analysis has occurred. It should also be noted that blood lactate samples taken in early studies were taken from the finger (55). More recent testing guidelines suggest that blood lactate samples are more reliable if taken from the earlobe (27).

Aerobic Capacity of Classical Ballet Dancers

Various authors have investigated the aerobic capacity of classical ballet dancers using laboratory-based maximal exertion tests. The results of these can be seen in Table 1, which also details maximal oxygen uptake of athletes participating in various sports.

Studies of whole ballet companies initially found that mean maximal oxygen uptake was higher in soloists (by 5%) than in members of the corps de ballet; however, this study only investigated soloists and corps de ballet and did not include any principal dancers (55). More recently, differences between dancer levels have been found, with principal dancers and artists having significantly greater relative peak O2 than first artists and soloists (p < 0.05) (60). This contradicts other studies (17) in which it was found that all dancers had similar cardiovascular profiles, regardless of rank in the company.

Initial investigations into aerobic capacity found that female ballet dancers had a mean O2max of 41.5 ± 6.7 ml·kg−1·min−1, whereas sedentary females of a similar age range had a mean O2max of 36.8 ± 5.5 ml·kg−1·min−1 (47). These results are supported by similar results (17) in which scores ranged from 40.9 to 50.9 ml·kg−1·min−1 for female dancers and 43.8 to 51.9 ml·kg−1·min−1 for male dancers. However, higher results were found in slightly later study that reported that the female dancers tested had a mean O2max of 48.6 ± 1.3 ml·kg−1·min−1, whereas males had a mean O2max of 59.3 ± 2.0 ml·kg−1·min−1 (46). A similar study reported slightly higher female values but lower male values than previously (46): 56 ml·kg−1·min−1 for male dancers and 51 to 53 ml·kg−1·min−1 for females (50). Recent findings sit within the range of results previously reported (47) in which female ballet dancers had a mean O2max of 50.22 ± 12.6 ml·kg−1·min−1 (48).

In a comparison between professional and university (USA) level female ballet dancers and professional and university (USA) level contemporary dancers, (15) it was found that professional ballet dancers had mean O2max scores of 42.2 ± 2.9 ml·kg−1·min−1. This study found that these scores were lower than both university level ballet dancers and both groups of contemporary dancers.

Cardiovascular adaptations to training and performance may also be seen when observing the heart using various cardiography tools such as those used by Cohen and colleagues (15). In this study, it was found that dancers have some changes to the heart as seen in other athletes such as sinus bradycardia, sinus arrhythmia, and left ventricular hypertrophy.

Muscular Power and Endurance

It has been suggested that there are 2 main requirements necessary for dancers; (32) one is a large reserve of power, required for explosive jumps and high elevation, which lasts just a few seconds, energized by phosphocreatine, and the other requirement suggested is muscular endurance, which occurs when a relatively high power output is maintained for 30 to 60 seconds. This could be, for example, in a series of jumps. This endurance can be measured by the amount of blood lactate that can be tolerated. It was reported that professional ballet dancers' peak blood lactate levels, following a Wingate test for anaerobic capacity, were lower than both university level ballet dancers and professional and training contemporary dancers (11). In this study, professional ballet dancers had a mean peak blood lactate level of 6.0 mmol ± 1.5, whereas university level ballet dancers had a mean level of 9.5 mmol ± 0.9. It was suggested that these low values indicate that professional ballet dancers have a low capacity to tolerate anaerobic exercise as compared with the other 3 groups. It may also be that the movement economy of professional ballet dancers is so efficient that this system is not challenged while dancing because a large percentage of the working day is devoted to honing technical skill. Because classical ballet has previously been described as a high-intensity, intermittent type of exercise, ideally, dancers ought to be able to tolerate exercise of this nature (17). This is supported by an investigation in which blood lactate levels reached up to 11 mM in performance, whereas during class, levels reached 3 mM (55). This may suggest that class is not sufficiently demanding to prepare dancers effectively for performance.

Another technique used to measure power in dancers is vertical jump height. A study of adolescent male ballet dancers (n = 27) reported a mean jump height of 31 cm (50), whereas a study of adolescent female ballet dancers (n = 22) reported a mean jump height of 32.4 ± 4.6 (12). Tests of professional dancers show a much greater jump height. This can be seen in Table 2 (60). Anaerobic power measurements of adolescent dancers have also been reported (49,50). Power in males, after a jumping test of 30 jumps, was reported as 9.5 ± 0.06 WKg−1 for prepubertal males and 10.7 ± 0.9 WKg−1 for pubertal males (50). Wingate testing in premenarcheal dancers resulted in average power of 6.6 ± 0.7 WKg−1 for vocational dancers (n = 24) and 6.2 ± 0.9 WKg−1 for recreational dancers (49).

Muscular Strength

Although enhancements in dance performance may occur as a result of an improvement in the force a muscle group can generate, (34) muscular strength has not generally been considered as a necessary ingredient for success in dance (32). Nevertheless, it has been found that dancers had greater hip external rotation strength (angle-specific torque) compared with nondancers, (25) whereas university level dancers lack strength of the hamstring muscle group, abdominals, the upper torso, arms, and the front of the lower leg (24). For instance, isokinetic dynamometry revealed that ballet dancers have lower muscular strength in the torso, quadriceps, and hamstrings compared with weight-predicted strength norms (29). This may be explained by the fact that dancers' skeletal muscle makes up approximately only two fifths of total body weight (61) and that their muscles have a high percentage (63% ± 12%) of type I muscle fibers (19).

Dancers may be wary of strength training because of fears that hypertrophy may occur, which, for aesthetic reasons, dancers are keen to avoid. It has been noted, nonetheless, that weight training can increase strength without necessarily resulting in hypertrophy because of neuromuscular adaptations (24). It has also been found that supplemental resistance training for hamstrings and quadriceps can lead to improvements in leg strength and dance performance without interfering with key artistic and physical performance requirements in male (30) and female (35) dancers.

Anthropometry

Low body fat and low waist-to-hip and waist-to-thigh ratios, seen among many dancers, are currently aesthetically favored by the dance profession (32). However, despite this trend, studies of the physiologic demands of classical ballet training, rehearsal, and performance, discussed previously (16,17,55), show that dancing has a low energy expenditure, which, when exacerbated by the high level of movement economy found in professional dancing, make maintaining aesthetic demands difficult to achieve. Consequently, the dietary intake of dancers, particularly females, may be restricted (4). It was reported that female classical ballet dancers tended to be, on average, only 75% of expected body weight (16). This restriction of nutrients has become recognized as a factor in delayed menarche, amenorrhea, or oligomenorrhea, the consequent loss of bone mineral density, which may be a predisposing factor in the occurrence of bone injury (13). The relationship between nutrient intake, body composition, and other dance injuries has not been so thoroughly investigated to date. One study reported that although there was no difference in injury rates between dancers with diets deemed within the study to be “adequate” and “inadequate,” those dancers with inadequate diets suffered more severe injuries and took longer to recover from them (4).

Somatotypes of trainee ballet dancers have been documented as endo-ectomorphic and meso-ectomorphic, with small girth values and lower body weights than nondancers (12). It has been found that adolescent ballet dancers were slimmer and taller compared with normative data (14). Compared with reference values, it was reported that these adolescent ballet dancers had smaller upper arms but larger calves and ankles, (11) both supporting and contradicting earlier findings (12). In a study of Japanese female ballet dancers, it was found that subjects had significantly lower body mass and percentage body fat measurements than nondancers, and, for all extremities, the percentage of muscle was significantly larger, and the percentage of adipose tissue was significantly smaller in the subject group (36).

Other studies have also shown that dancers have low body fat (9,44,48,56,57). It has been recommended (9) that between 17% and 23% body fat is optimum for adult university level female dancers; however, several studies have found that professional ballet dancers have mean body fat percentages varying from 14% (48) to 17-19% (44,56,57,61). Several of these studies were conducted using various testing techniques, for example, bioelectrical impedance analysis (BIA), hydrostatic weighing, dual x-ray absoptiometry (DXA), and skinfold thickness measurements. One such study (61) found that skinfold measurements were the least accurate (n = 42 females, mean age of 21 ± 2 yr); however, another found no significant differences between BIA and skinfolds but a significant difference between DXA and skinfolds (n = 24 female, mean age 22.6 ± 4.5 yr) (57). A similar study found that skinfold measurements were positively correlated with both BIA and DXA measurements, supporting previous findings related to BIA but contradicting those regarding DXA (20). This study also had the largest sample size (n = 59 female) but was conducted on adolescent (age 14-17 yr) dancers. Results of these studies can be seen in Table 4. The differences in sample sizes and ages between these studies may explain some of the variation in results. Recent work (59) reviewed many research articles regarding the various methods of body composition analysis and advised that there are error margins to be considered with every method and that researchers comparing studies using different methodologies should take these error margins into consideration.

Flexibility

It has been documented that classical ballet dancers have greater than normal flexibility in most lower-extremity joints (53). An investigation reported that dancers have supernormal ankle plantar flexion but that this was accompanied by diminished ankle dorsiflexion (16). Ballet dancers are more flexible in passive hip external rotation, flexion, abduction, and knee extension than nondancers but have less range of motion in passive hip adduction and internal rotation. Furthermore, this pattern is more pronounced in more experienced dancers, suggesting that it may be a direct result of dancing itself (53). A study involving students found that ballet students have a higher degree of hip flexibility than nondancing students of a similar age (12). The need for this range of motion has been reinforced by suggesting that dancers who use a turn-out position that exceeds their available passive range of motion of external hip rotation are more prone to injury (18). Dancers, because of the demands of ballet technique, are also required to have greater than normal hyperextension of the spine and flexible hamstrings and abductors (43). A recent comparison study also found that dancers had significantly greater inner hip external rotation than nondancers (54° ± 2°, and 47° ± 2°, respectively, p = 0.013) (25). The flexibility of 30 ballet dancers was assessed using the “Sit and Reach” test (48); the ballet dancers' mean flexibility scores were 22.8 cm ± 4.12. This was compared with folk dancers, who scored 12.41 cm ± 6.46. Other data regarding flexibility in both ballet and contemporary dancers can be seen in Table 5.

Agility

There appears to be little published information regarding agility in classical ballet. An early study into the effects of various fitness components on modern dance performance did not find a significant relationship between agility and performance; however, the methodology used to determine performance was nonstandardized, and the number of subjects is unknown (6). It has been suggested that ballet had higher demands on agility and balance than football, basketball, hockey, and baseball; however, this information was subjective and anecdotal (54). Another study (2) found that dance training significantly increased the agility of cross-country skiers who participated in dance training supplementary to cross-country skiing. In this study, agility was tested using a hurdle-test in which subjects jumped over and climbed under hurdles and were timed.

Summary

In terms of the demands of classical ballet, there appears to be some consensus on performance being a high-intensity, intermittent form of exercise; however, compared with other high-intensity, intermittent sports, the literature reviewed has indicated that dancers have poorly developed physical parameters. This poor underlying physiology may account for the high injury rates seen in classical ballet. The second national enquiry into dancers' health and injury in the United Kingdom (37) reported that 85% of professional ballet dancers reported at least 1 injury within 12 months. Over 50% of these injuries were to muscle, 50% were to joints, over 20% were tendon related, 15% were bone related, and over 5% were reported as “other.” (37) Potentially, the dancers' neglected physical foundations, slightly offset by their highly developed economy of movement, leave them susceptible to fatigue. This is turn has an effect on skill, causing poor alignment, especially during landing and lifting, and thereby exposing the body to inappropriate shear and rotational forces, increasing risk of injury. This differentiates classical ballet from sports in which athletes have a good reserve of physical fitness to “fall back on” should problem with skill arise. It has been reported that dancers do not have this reserve (1). Therefore, once skill decreases because of fatigue, injury becomes more likely (1).

Because classical ballet is still dictated largely by artistic and aesthetic principles, ballet teachers, choreographers, and artistic directors appear reticent to include regular supplemental training into a dancers' schedule. Although it has been hypothesized that increased fitness may reduce injury rate, there are still concerns that supplemental training will affect the aesthetics of classical ballet dancers and their performance. There has been some increase in the use of body-conditioning interventions such as Pilates, Feldenkrais, and Alexander technique, and these are popular among dancers. However, they have generally received little scientific validation (25).

This review has shown that dance science literature to date has more emphasis on the aerobic demands of ballet, the aerobic capacity of dance, and, perhaps because of the aesthetic nature of classical ballet, body composition has also been investigated more thoroughly than other aspects of fitness such as agility and flexibility. Results in many of the studies have differed, leading to the conclusion that more research on the subject needs to be carried out.

Research into the demands of classical ballet indicates that it poses the same cardiorespiratory demands as similar high-intensity, intermittent sports. However, there has been little scientific investigation into other demands of classical ballet performance such as strength, power, speed, agility, and flexibility. Before dance scientists and strength and conditioning specialists can attempt to design interventions to improve performance, and to enhance fitness and wellbeing of dancers, the demands of classical ballet performance must be more thoroughly ascertained.

Practical Applications

It is suggested that the way a dancer is trained, especially within a company environment, needs to be reviewed. That dance is a skill-based artistic format is not being questioned, but unless the “physiologic dancer” is honed to the same extent as the “artistic dancer,” then, for the latter, the limiting factor within their performance capabilities will potentially be their physical conditioning. Presently, most companies have morning class followed by rehearsals or performances. The concept of additional supplemental training to their already busy schedules is impractical and would possibly increase the injury rate and occurrence of overtraining. The substitution of 2 to 3 dance classes a week with physical conditioning classes would have a beneficial effect on the dancers underlying physical fitness without interfering or causing a deterioration of skill; there should be enough skill reinforcement within 2 classes a week, rehearsals, and performances to maintain skill levels, although this has not been examined. The conditioning classes could easily use dance movements to elicit a training effect by lengthening the dance periods during center work and reducing the rest time. The emphasis would need to be on training effect rather than movement accuracy because, otherwise, the training benefits would be lost. Other research studies have noted subsequent benefits of supplemental training, including increased strength and active flexibility (7,21,22,28,31,41). The need for these sessions to take the place of dance class and not be additional training is emphasized in a study that noted increases in dancers' fitness levels during a holiday period during which they were not active, suggesting that before the start of the holiday they were overtrained (33).

52. Redding, E and Wyon, MA. Differences between active and passive flexibility in dancers' extension a la seconde in classical ballet and contemporary dancers. In: Proceedings of the International Association of Dance Medicine and Science, San Francisco, 2004.